- ID:
- ivo://CDS.VizieR/J/ApJS/208/9
- Title:
- Intrinsic colors and temperatures of PMS stars
- Short Name:
- J/ApJS/208/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the intrinsic colors and temperatures of 5-30 Myr old pre-main-sequence (pre-MS) stars using the F0- through M9-type members of nearby, negligibly reddened groups: the {eta} Cha cluster, the TW Hydra Association, the {beta} Pic Moving Group, and the Tucana-Horologium Association. To check the consistency of spectral types from the literature, we estimate new spectral types for 52 nearby pre-MS stars with spectral types F3 through M4 using optical spectra taken with the SMARTS 1.5 m telescope. Combining these new types with published spectral types and photometry from the literature (Johnson-Cousins BVI_C_, 2MASS JHK_S_ and WISE W1, W2, W3, and W4), we derive a new empirical spectral type-color sequence for 5-30 Myr old pre-MS stars. Colors for pre-MS stars match dwarf colors for some spectral types and colors, but for other spectral types and colors, deviations can exceed 0.3 mag. We estimate effective temperatures (T_eff_) and bolometric corrections (BCs) for our pre-MS star sample through comparing their photometry to synthetic photometry generated using the BT-Settl grid of model atmosphere spectra. We derive a new T_eff_ and BC scale for pre-MS stars, which should be a more appropriate match for T Tauri stars than often-adopted dwarf star scales. While our new T_eff_ scale for pre-MS stars is within =~100K of dwarfs at a given spectral type for stars <G5, for G5 through K6, the pre-MS stars are ~250 K cooler than their MS counterparts. Lastly, we present (1) a modern T_eff_, optical/IR color, and BC sequence for O9V-M9V MS stars based on an extensive literature survey, (2) a revised Q-method relation for dereddening UBV photometry of OB-type stars, and (3) introduce two candidate spectral standard stars as representatives of spectral types K8V and K9V.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/733/113
- Title:
- IRAC observations of IC 1795
- Short Name:
- J/ApJ/733/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep Spitzer/Infrared Array Camera (IRAC) survey of the OB association IC 1795 carried out to investigate the evolution of protoplanetary disks in regions of massive star formation. Combining Spitzer/IRAC data with Chandra/Advanced CCD Imaging Spectrometer observations, we find 289 cluster members. An additional 340 sources with an infrared excess, but without X-ray counterpart, are classified as cluster member candidates. Both surveys are complete down to stellar masses of about 1M_{sun}_. We present pre-main-sequence isochrones computed for the first time in the Spitzer/IRAC colors. The age of the cluster, determined via the location of the Class III sources in the [3.6]-[4.5]/[3.6] color-magnitude diagram, is in the range of 3-5Myr. As theoretically expected, we do not find any systematic variation in the spatial distribution of disks within 0.6pc of either O-type star in the association. However, the disk fraction in IC 1795 does depend on the stellar mass: sources with masses >2M_{sun}_ have a disk fraction of ~20%, while lower mass objects (2-0.8M_{sun}_) have a disk fraction of ~50%. This implies that disks around massive stars have a shorter dissipation timescale.
- ID:
- ivo://CDS.VizieR/J/ApJ/752/127
- Title:
- IR observations of AFGL 490
- Short Name:
- J/ApJ/752/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer IRAC and MIPS observations of the star-forming region containing intermediate-mass young stellar object (YSO) AFGL 490. We supplement these data with near-IR Two Micron All Sky Survey photometry and with deep Simultaneous Quad Infrared Imaging Device observations off the central high-extinction region. We have more than doubled the known membership of this region to 57 Class I and 303 Class II YSOs via the combined 1-24{mu}m photometric catalog derived from these data. We construct and analyze the minimum spanning tree of their projected positions, isolating one locally overdense cluster core containing 219 YSOs (60.8% of the region's members). We find this cluster core to be larger yet less dense than similarly analyzed clusters. Although the structure of this cluster core appears irregular, we demonstrate that the parsec-scale surface densities of both YSOs and gas are correlated with a power-law slope of 2.8, as found for other similarly analyzed nearby molecular clouds. We also explore the mass segregation implications of AFGL 490's offset from the center of its core, finding that it has no apparent preferential central position relative to the low-mass members.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A66
- Title:
- IR photometry in UKIDSS sigma Orionis stars
- Short Name:
- J/A+A/608/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for new planetary mass objects by combining our deep I-band photometry with public J-band magnitudes and by examining the nearby environment of known very low mass members for possible companions. Our analysis confirms the existing census of substellar cluster members down to approximately 7M_Jup_.
- ID:
- ivo://CDS.VizieR/J/A+A/397/177
- Title:
- IR star clusters and stellar groups catalog
- Short Name:
- J/A+A/397/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compiled a catalogue of infrared star clusters in the Galaxy, which are most of them embedded. It condenses the growing literature information. We also include in the sample infrared stellar groups which are less dense than star clusters, such as those embedded in the dark clouds Taurus-Auriga and Chamaleon I. We provide galactic and equatorial coordinates, angular dimensions, different designations and related objects such as nebulae. A total of 189 infrared clusters and 87 embedded stellar groups are included. A fraction of 25% of the embedded clusters are projected close to each other in pair or triplet systems, indicating that multiplicity plays an important role in star cluster formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/470/864
- Title:
- JHKL photometry of the Galactic Center
- Short Name:
- J/ApJ/470/864
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- J, H, K, and L photometry for the stars in the central ~2' (~5pc) of the Galaxy are presented. Using the observed J-H, H-K, and K-L colors and assumed intrinsic colors, we determine the interstellar extinction at 2.2mm (A_K_) for approximately 1100 individual stars. The mean A_K_ (=3.3mag) is similar to previous results, but we find that the reddening is highly variable, and some stars are likely to be seen through A_K_>6mag. The dereddened K-band luminosity function points to a significantly brighter component to the stellar population (>1.5mag at K) than found in the stellar population in Baade's window, confirming previous work done at lower spatial resolution. The observed flux of all Galactic center stars with estimated K0 (dereddened magnitude) =<7.0mag is ~25% of the total in the 2'x2' field. The data were obtained in July 11-13 on the 4m telescope at the Cerro Tololo Observatory (CTIO) using the Ohio State Infrared Imager qnd Spectrometer (OSIRIS). Our observations confirm the recent finding that several bright M stars in the Galactic center are variable. Our photometry also establishes the near-infrared variability of the M1-2 supergiant, IRS 7.
- ID:
- ivo://CDS.VizieR/J/A+A/461/949
- Title:
- JHK photometry around IRAS 09149-4743
- Short Name:
- J/A+A/461/949
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a near-infrared survey of the young stellar cluster associated with IRAS 09149-4743, a member of the Vela Molecular Ridge. The main purpose of this survey is to study the cluster members and find the ionizing sources of the associated HII region.
- ID:
- ivo://CDS.VizieR/J/A+A/361/660
- Title:
- JHK photometry around S233IR
- Short Name:
- J/A+A/361/660
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observed properties of sources in the region S233IR in a field of 3.1 arcmin by 3.1 arcmin, which contains two young stellar clusters located to the northeast (NE) and southwest (SW) of the field center (RA = 05 35 49.79, DE = +35 44 01.9). Source positions, JHK photometry, extinction and estimated stellar mass are provided.
- ID:
- ivo://CDS.VizieR/J/PASP/120/150
- Title:
- JHK photometry in Cluster [BDS2003] 107
- Short Name:
- J/PASP/120/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new near-infrared classification spectra for nine candidate members of the galactic cluster [BDS2003] 107 (Cluster 107) observed with the IRTF SpeX instrument. We can spectroscopically classify at least three members, two of which have published 2MASS photometry. These two stars provide preliminary values for the approximate age (10^6^yr), distance (<=2kpc), and extinction (A_V_~23) of the young cluster. Based on the properties of the brightest members we have identified, on the surface Cluster 107 appears to be very similar to the well-studied Orion cluster. We find a single mid-O dwarf star and a number of early-B stars, along with massive young stellar objects (YSOs) in the field. The massive YSO Star 63 shows simultaneously an early-B spectral classification in the short K-band with CO band-head emission at 2.3um. This massive YSO looks similar to other luminous CO emission objects seen in young, massive clusters through out the Galaxy and provides additional evidence for the existence of circumstellar disks around even fairly massive stars. Several previously identified radio sources, presumably associated with very early star formation, lie within this field, three of which appear to have near-infrared counterparts as detected in images we obtained with the SpeX acquisition camera.
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/1185
- Title:
- JHK photometry in 2 star-forming regions
- Short Name:
- J/MNRAS/390/1185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS 21413+5442 and IRAS 21407+5441 are two massive star-forming regions of high luminosity, likely associated with each other. Near-infrared (NIR) photometry on these two IRAS sources was performed at United Kingdom Infrared Telescope (UKIRT) using the UFTI under excellent seeing conditions yielding an angular resolution of ~0.5arcsec. Our results reveal details of stellar content to a completeness limit (90 per cent) of J=18.5, H=18.0 and K=17.5mag in the two regions. In IRAS 21413+5442, we identify a late O-type star, having large H-K colour, to be near the centre of the CO jets observed by earlier authors. The UKIRT images reveal in IRAS 21407+5441, a faint but clear compact HII region around a central high- and intermediate-mass star cluster. We have detected a number of sources with large H-K colour which are not detected in J band. We also present the GMRT radio continuum map at 1.28GHz covering the entire region surrounding the two star-forming clouds.
